Question 1: The background information presented to the SAP panel by the FEMS developers provides both user guidance and a technical overview of the system. Is this document sufficiently detailed and understandable? Are the descriptions of the specific model components scientifically sound? Do the algorithms in the annotated code perform the functions as defined in this document? Were the panel members able to load the software and evaluate the system including the presented case study?

Critical Element 2: System Design/Inputs

Question 2: In Section 2.1: Overview of Conceptual Model of the background document, a series of flowcharts (Figures 2, 3, and 4) are presented that detail the individual processes and components that are included in FEMS. The key processes include (1) emissions processing, (2) 200 year weather inputs and how they are used for longer-term Monte-Carlo sampling; and (3) TOXST analysis. What can the panel say about these proposed processes, the nature of the components included in FEMS and the data needed to generate an analysis using FEMS? Are there any other potential critical sources of data or methodologies that should be considered?

Question 3: The determination of appropriate flux/emission rates is critical to the proper use of the FEMS model as these values define the source of fumigants in the air that can lead to exposures. There are different methods of determining flux/emission rates from empirical data including direct measurements and what is referred to as the “indirect” or “back-calculation” method. Direct measurement of flux is not that common in the available data because of the difficulties and expense associated with generating these types of data. The “indirect” method is most commonly used and involves fitting monitoring data with ISC to determine flux/emission rates. Upon its review of how flux rates can be calculated, the Agency has identified a number of questions it would like the panel to consider. The emission fitting procedures used in FEMS are based on least squares analyses of log-transformed, dispersion modeling and field monitoring data. What, if any refinements are needed for this process? Is it appropriate to log transform these types of data for back-calculation purposes and to use a least-squares regression analysis which implicitly assumes that the fitted line passes through the origin? How appropriate is it to use a flux/emission factor from a single monitoring study (or small number of studies) and apply it to different situations such as for the same crop in a different region of the country? Does the panel believe that FEMS could adequately consider multiple, linked application events as well as single source scenarios? Does FEMS appropriately address situations where data are missing (i.e., is the data filling procedure appropriate)? Should there be a threshold r2 value below which a regression of measured versus modeled air concentrations should not be used in flux rate determinations? What are possible alternative approaches?

10:00 AM BREAK

10:15 AM Panel Discussion (continued)

Question 4: The integration of actual time-base meteorological data into ISCST3 is one of the key components that separates the FEMS methodology from that being employed by the Agency in its current assessment. The Agency has identified several potential sources of these data including the National Weather Service, Federal Aviation Administration, California Irrigation Management Information System (CIMIS), and the Florida Automated Weather Network (FAWN). The Agency is also aware that there are several approaches that can be used to process meteorological data and acknowledges that FEMS used PCRAMMET which is a standard Agency tool for this purpose. Upon its review of what meteorological data are available and how it can be processed for use in an assessment such as this, the Agency has identified a number of questions it would like the panel to consider. The test case example in FEMS is based on the National Weather Service ASOS meteorological monitoring station in Fresno, California. What are the SAP’s thoughts on the use of National Weather Service / Federal Aviation Administration meteorological data sets in comparison with either CIMIS or FAWN for this type of application? What criteria should be used to identify meteorological regions for analysis and how should specific monitoring data be selected from within each region? Anemometer sampling height has been identified as a concern by the Agency in preparation for this meeting. For example, some data are collected at 2 meters while others are collected at a height of 10 meters. What are the potential impacts of using either type of data in an analysis of this nature? FEMS uses “assumed distributions” to account for uncertainty in the meteorological data based on Hanna, 1998 [as referenced in the FEMS background paper]. Is this an appropriate technique? Does FEMS treat stability class inputs appropriately, especially the quantitative manipulations of these data that have been completed? Is the concurrent use of emissions and meteorological conditions in FEMS useful in identifying concurrent upper-end conditions that could lead to peak exposures for bounding exposure events?

Question 5: The Agency model, ISCST3 is the basis for the FEMS approach. This model has been peer reviewed and is commonly used for regulatory purposes by the Agency. FEMS also uses other Agency systems such as PCRAMMET and TOXST. Are there specific recommendations that the panel can make with regard to any parameter that should be altered to optimize the manner that they are used in FEMS? ISCST3 can treat “calm” (i.e., periods where the windspeed in essentially 0) in one of two ways including the concentration is set to (0) and an approach that uses the last non-calm wind direction/concentration. FEMS uses the first approach. Does the panel concur? In Section 2.2 Specific Technical Considerations With Regard To The Design Of FEMS of the background document, there is a section entitled Computing Endpoint Distances. Please comment on the procedures included in this section? The FEMS analysis is based on a single field being treated once per year. On this basis, ISCST3 files include 200 full years of hour-by-hour sequential data. Application start times are randomly selected to match the user-supplied application frequency. For example, if a model user entered 10,000 simulations, there will be approximately 10,000 randomly selected start times with batch modeling treatment of 4 days duration for each application. In addition, FEMS allows for more than one application per year to be modeled. Does the panel view this as an appropriate process? If not can it make suggest recommendations or modifications that may improve this process? Can the panel comment on the source geometry used in FEMS and the implications of this choice?

12:00 PM LUNCH

1:00 PM Panel Discussion (continued)

Critical Element 3: Results

Question 6: Soil fumigants can be used in different regions of country under different conditions and they can be applied with a variety of equipment. Does the SAP believe that the methodologies in FEMS can be applied generically in order to assess a wide variety of fumigant uses? What considerations with regard to data needs and model inputs should be considered for such an effort?

Question 7: Does FEMS adequately identify and quantify airborne concentrations of soil fumigants that have migrated from treated fields to sensitive receptors? The Agency is particularly concerned about air concentrations in the upper ends of the distribution. Are these results presented in a clear and concise manner that would allow for appropriate characterization of exposures that could occur at such levels?

Question 8: A sensitivity analysis has been conducted and is described in the FEMS background document. What types, if any, of additional contribution/sensitivity analyses are recommended by the panel to be the most useful in making scientifically sound, regulatory decisions? What should be routinely reported as part of a FEMS assessment with respect to inputs and outputs? Are there certain tables and graphs that should be reported? What types of further evaluation steps does the panel recommend for FEMS?

5 :00 PM ADJOURNMENT

Please be advised that agenda times are approximate. For further information, please contact the Designated Federal Official for this meeting, Mr. Paul Lewis, via telephone: (202) 564-8450; fax: (202) 564-8382; or email: lewis.paul@epa.gov